missflo 0 Report post Posted July 28, 2019 Hello all : ) I just bought some cobalt oxide, I'd like to paint it directly on some leather hard stoneware vessels before bisque. Can I ask if anyone knows which percentage of cobalt to amount of water should I use for best results? Thank you! Quote Share this post Link to post Share on other sites
Mark C. 3,894 Report post Posted July 28, 2019 (edited) Just mix a bit in a small amount of water (I never measure it) Just make sure its a strong dark mix. Edited July 28, 2019 by Mark C. Quote Share this post Link to post Share on other sites
missflo 0 Report post Posted July 28, 2019 great thanks! Quote Share this post Link to post Share on other sites
Babs 939 Report post Posted July 29, 2019 KIf just starting out on this you could make different dilutions to see how it turns out. Some mix the cobalt oxide with a little iron oxide for a softer blue. Cobalt oxide ,a strong colourant, little goes a long way. What is your next move? Clear glaze? White glaze? Should make a tile with stripes of your strengths of CoO 1 MFP reacted to this Quote Share this post Link to post Share on other sites
oldlady 2,420 Report post Posted July 30, 2019 just FYI, cobalt oxide can sometimes leave tiny specks of really dark color wherever you apply it. cobalt carbonate is more easily dispersed in water or slip or whatever you like as a medium. 2 liambesaw and Babs reacted to this Quote Share this post Link to post Share on other sites
Brandon Franks 30 Report post Posted July 30, 2019 On 7/28/2019 at 11:46 AM, missflo said: Hello all : ) I just bought some cobalt oxide, I'd like to paint it directly on some leather hard stoneware vessels before bisque. Can I ask if anyone knows which percentage of cobalt to amount of water should I use for best results? Thank you! I haven't used cobalt oxide, but for my blue slip, I use 97.5% porcelain and 2.5% cobalt carb. I put sodium silicate in and find that it works really well. The water ration for this slip never matters as long as it isn't super, super fluid. I used to just do oxide+water on leather hard pieces, but find the slips to work much better. Quote Share this post Link to post Share on other sites
Mark C. 3,894 Report post Posted July 30, 2019 I agree that cobalt crab is a bit more refined and does a better job with no extra strong blue spots. I have some mixed in a jar of water for the past 40 years it evaporates and I just add a bit of water when needed. I use it to draw and band a few pots a year. Quote Share this post Link to post Share on other sites
missflo 0 Report post Posted July 31, 2019 wonderful, this is so kind of you all, I'm very excited to try cobalt tomorrow and hopefully cobalt carb too in the near future Quote Share this post Link to post Share on other sites
Hulk 427 Report post Posted July 31, 2019 Isn't the carbonate safer? Quote Share this post Link to post Share on other sites
liambesaw 1,845 Report post Posted July 31, 2019 9 minutes ago, Hulk said: Isn't the carbonate safer? In what way? It decomposes to cobalt oxide in the kiln, so after firing it will be as safe as cobalt oxide. Quote Share this post Link to post Share on other sites
Hulk 427 Report post Posted July 31, 2019 I'm not finding the reference just now, thought that oxide is soluble, carbonate is not - in terms of handling the powder, not after firing... Quote Share this post Link to post Share on other sites
Brandon Franks 30 Report post Posted July 31, 2019 34 minutes ago, Hulk said: I'm not finding the reference just now, thought that oxide is soluble, carbonate is not - in terms of handling the powder, not after firing... 34 minutes ago, Hulk said: I'm not finding the reference just now, thought that oxide is soluble, carbonate is not - in terms of handling the powder, not after firing... I rule is to not eat on an unglazed surface that has colorants on it. Quote Share this post Link to post Share on other sites
liambesaw 1,845 Report post Posted July 31, 2019 45 minutes ago, Hulk said: I'm not finding the reference just now, thought that oxide is soluble, carbonate is not - in terms of handling the powder, not after firing... I see, well they are both insoluble in water, but the carbonate is a salt, it's just less concentrated than the oxide. I think it's important to use caution with both 1 Hulk reacted to this Quote Share this post Link to post Share on other sites
Babs 939 Report post Posted August 1, 2019 9 hours ago, Hulk said: I'm not finding the reference just now, thought that oxide is soluble, carbonate is not - in terms of handling the powder, not after firing... Think the soluble one is cobalt sulphate or nitrate. Think some folk use it as onglaze washes. Not to be played with 1 Hulk reacted to this Quote Share this post Link to post Share on other sites
MFP 31 Report post Posted August 12, 2019 Another option is cobalt alumina...it's a bright blue and easy to see how much you are using. I used to use the cobalt oxide to do Chinese brush on pots.....on the glaze. It needed to look like the ink would look if you were doing the drawing on paper....that was my guide. I liked it better than carbonate because I could see the result better than with the carbonate. 1 Hulk reacted to this Quote Share this post Link to post Share on other sites
preeta 207 Report post Posted August 20, 2019 In cases where you cant see the color food coloring is your friend. 1 Hulk reacted to this Quote Share this post Link to post Share on other sites
